package Leetcode;

import java.util.ArrayList;

import java.util.HashMap;

import java.util.List;

class TreeNode

{

int val;

TreeNode left;

TreeNode right;

TreeNode( int x )

{

val = x;

}

}

public class RightViewOfTree

{

public static List<Integer> rightSideView( TreeNode root )

{

List<Integer> result = new ArrayList<Integer>();

HashMap<Integer, Integer> map = new HashMap<>();

viewHelper( root, result, map, 0 );

return result;

}

private static void viewHelper( TreeNode root, List<Integer> result, HashMap<Integer, Integer> map, int level )

{

if( root == null )

return;

if( !map.containsKey( level ) )

{

map.put( level, root.val );

result.add( root.val );

}

viewHelper( root.right, result, map, level + 1 );

viewHelper( root.left, result, map, level + 1 );

}

public static void main( String[] args )

{

TreeNode root = new TreeNode( 1 );

root.left = new TreeNode( 2 );

root.right = new TreeNode( 3 );

root.left.left = new TreeNode( 4 );

List<Integer> result = RightViewOfTree.rightSideView( root );

for( Integer number : result )

System.out.println( number );

}

}